In this fiscal year, we completed numerous clinical projects involving myositis patients. These projects included: (a) Analyzing a longitudinal cohort of pediatric myositis patients with anti-NT5C1a autoantibodies. Among other observations, this published study established that anti-NT5C1a autoantibodies are found in children with myositis and juvenile idiopathic arthritis. In children with myositis, anti-NT5C1a autoantibodies are associated with more severe disease. (b) Studying the development of myositis in patients treated with immune checkpoint inhibitors. We published a study showing that pre-existing anti-acetylcholine receptor autoantibodies and B cell lymphopaenia are associated with the development of myositis in patients with thymoma treated with avelumab, an immune checkpoint inhibitor targeting programmed death-ligand 1. (c) Defining unique phenotypes associated with distinct myositis autoantibodies. Using a longitudinal cohort of adult myositis patients, we published an paper showing that patients with anti-PM/Scl autoantibodies have a unique pattern of muscle involvement with prominent perivascular inflammation on muscle biopsy and proximal arm muscles weaker than proximal leg weakness on physical exam. These patients also have extensive extra-muscular manifestations including interstitial lung disease. In collaboration with Dr. Lisa Rider, Dr. Fred Miller, and their colleagues at NIEHS, we have sought to determine the phenotype of pediatric myositis patients with anti-Ro52 autoantibodies. We found that children with myositis who have anti-Ro52 autoantibodies are more likely to have interstitial lung disease. We have presented these findings at national meetings and are now preparing a manuscript for publication.